Filters of the type used for filtering particulate matter from engine intake air sometimes include one or more layers of a porous filter material that is formed into a convoluted pattern, often referred to in the industry as fluted filter media. One type of porous filter material commonly used for such filters is a cardboard or paper-type material having a thickness in the range of 0.006 to 0.008 inches. This material is somewhat stiff, and not easily bent or formed, without special provisions being made to prevent tearing or breaking the material. Although it is desirable to use a media of this type having a greater thickness, in the range of 0.012 to 0.018 inches for example, such thicker media has not been used in the past due to difficulties inherent in forming such stiff materials into a compact convoluted shape.
In the past, such fluted filter media was typically formed by processes which required, or resulted in the porous filter material being at least locally compressed during the process of forming the convolutions. Compression of the porous filter media is undesirable because it reduces the filtering efficiency and particulate holding capacity of the fluted filter media below what it could be if the porous filter media could be formed into a convoluted shape without compression of the media. The degree and unavoidability of such compression in the past would have essentially negated any advantage gained by using a thicker media, even if the problem of breakage or tearing could have been resolved.
In one widely utilized prior approach to forming a convoluted media, the porous filter material is fed through a corrugating machine, between a pair of rollers having intermeshing wavy surfaces which pinch and crimp the porous media in a manner that compresses and permanently deforms the filter media into a convoluted shape that is generally self supporting, and able to maintain the convoluted shape following corrugation, regardless of whether or not the corrugations are constrained. United States patent application number US 2003/0121845 A1, to Wagner, et al, discloses such an approach.
Corrugation typically compresses the porous filter material by 25 to 40 percent from its thickness prior to being corrugated, resulting in a significant reduction in efficiency and effectiveness, particularly where the media prior to corrugating has a thickness only in the range of 0.006 to 0.008 inches. It is also typically necessary, for paper filter media of the type often used in air filters, to expose the porous filter media to a water spray, steam, and heat, during the corrugation process in order to achieve a corrugated product that is self supporting. These additional processing requirements add undesirable cost and complexity to the manufacture of corrugated filter media, and exacerbate compression of the filter media during corrugation.
In another widely utilized prior approach to forming a fluted filter media, the porous material is pleated, rather than corrugated, by first feeding a sheet of porous media between a pair of cylinders or toothed belts having ridges which locally compress the porous material at periodic intervals, to thereby crease or score the material. The scored material is then fed through a folding mechanism which causes the scored media to fold at the scoring into a pleated shape. Such pleated shapes are not generally as self supporting as corrugated media, requiring that the pleats be constrained and held in an equally spaced relationship by a spacing mechanism, until they can be joined to a face sheet or secured to a support structure. U.S. Pat. Nos. 4,798,575 and 4,976,677 to Siversson, U.S. Pat. No. 5,389,175 to Wenz, and U.S. Pat. No. 6,022,305 to Choi, et al, disclose such pleated methods and pleated filter media. Where it is desired to set the pleats into a self supporting form, liquids sprayed onto the porous media, and sequentially applied heating and cooling are sometimes utilized, in the same manner described above in relation to corrugated filter media.
As was the case with corrugated media, in pleated media the scoring undesirably reduces the thickness of the porous media, thereby reducing its filtering effectiveness and efficiency. Also, the mechanisms required for sequentially scoring, forming, spacing, spraying, heating and cooling the pleated media undesirably increase the complexity and cost of manufacturing the pleated media.
It is desirable, therefore, to provide an improved filter media, together with an apparatus and method for manufacturing such an improved media. It is also desirable to provide an improved filter apparatus incorporating such an improved filter media.